Niagara’s Innovative 0.8 gpf “Vacuum-Assist” Stealth Toilet

A new toilet from Niagara pioneers a radically new flush technology--and uses just half as much water as standard toilets.

Posted on May 21 2010 by Alex Wilson

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While looking much like a standard toilet, there are big differences in the Niagara Stealth toilet. One difference is an air-transfer tube cast into the porcelain leading from the tank to the trapway--which can be seen near the back of the toilet.

Niagara Conservation has introduced a new toilet that's unlike anything on the market. It uses passive "vacuum-assist" technology to deliver a very quiet, effective flush that consumes just 0.8 gallons (3.0 liters)--making it, I believe, the most water-conserving of any flush toilet on the market.

Who knew there would be so many ways to flush a toilet!

While pressure-assist toilets use compressed air at the top of a sealed tank to push water through the flush valve at a high velocity (achieving a very effective flush), the vacuum-assist Stealth toilet literally pulls the contents of the toilet bowl down the trapway from below.

Here's how it works:

After the toilet is flushed, water fills a special inner chamber that's hidden inside the conventional-looking toilet tank. (In this respect, it is like a pressure-assist toilet--with its tank-within-a-tank that is filled from the bottom.) As this inner chamber fills, though, air at the top is pushed down through a special transfer tube into the trapway, essentially creating a large air bubble between water in the toilet bowl and water in the sanitary trap near the base of the toilet (see the first diagram). This air bubble, which fills about 12 inches of the trapway, exerts a force on the water in the trapway, raising the water level in the toilet bowl to create a larger water spot (water surface area) than would be expected from a toilet using just 0.8 gallons per flush.

When the toilet is flushed, water exiting the inner chamber creates a vacuum--depressurizing the trapway. This depressurization creates a suction force that pulls water from the toilet bowl into the trapway. During the flush, the trapway is entirely filled with water, which cleans the fully glazed trapway.

The vacuum-assist flush mechanism helps the toilet effectively flush a significant quantity of waste using very little water. Using the now-industry-standard Maximum-Performance (MaP) testing protocol, the Stealth toilet is rated at 600 grams, in both the round-front and elongated-front models. This and other performance features have allowed the toilet to earn the EPA WaterSense label for high-efficiency toilets. According to Cecilia Hayward, the marketing manager at Niagara, the toilet also passes all IAPMO requirements for toilets, including a requirement that waste be effectively moved 40 feet along the drainline when the toilet is flushed.

Pressure-assist toilets are popular, because the extra force on the flush does an excellent job at evacuating the toilet bowl and waste in it, and some of these toilets do so with just 1.0 gpf. But pressure-assist toilets are louder than gravity-flush toilets, producing a characteristic "whoosh" during the flush. To an unsuspecting user, they can be quite startling.

The vacuum-assist mechanism in the (aptly named) Stealth toilet avoids that noise. According to Bill Gauley, P.Eng., principal of Veritec Consulting in Mississauga, Ontario (and the co-developer of the MaP testing protocol for toilets), "it is no louder than any other gravity-flush toilet--and much quieter than a pressure-assist toilet."

According to Chris Hanson, who is president of AquaPro Solutions, a water products distribution company and director of the Aqua Environmental Resource Center, both in Ashville, North Carolina, the toilet performs even better in his own MaP tests--consistently removing 800 grams of test media. He has one of the toilets that he's been testing off-and-on for about eight months, and the toilet has also been installed some of that time in the Resource Center--where it has worked without incident. He told me that it's not only quieter than pressure-assist toilets, but also quieter than most gravity-flush toilets, including Niagara's own Flapperless toilet.

One issue to be aware of, according to Hanson, is that because so little water is used for the flush (half the federal maximum), waste may not be conveyed as far as with toilets that have higher flush-volume. He suggests installations where the "horizontal run" will be no more than about 20 feet, before reaching a vertical stack.

Regarding waste conveyance, Gauley said, "I would not be concerned installing this toilet in any residential situation, though I would not recommend it at this time in non-residential installations."

The Niagara Stealth toilet was first introduced in a soft launch in the fall of 2009, but the formal launch was at the Kitchen & Bath Industry Show (KBIS) in April 2009.

The Stealth carries a manufacturer's suggested list price of $310 in the round-front model and $325 in the elongated front model. The product is proving popular, according to Hayward, who estimates that up to 1,000 have already been sold.

In the U.S. Niagara is the exclusive manufacturer of toilets using this technology, while in Canada the same mechanism is used in Proficiency toilets made by Hennessy & Hinchcliffe (the company that invented the Stealth flush technology as well as Niagara's Flapperless technology). Hennessy & Hinchliffe and Niagara are business partners and collaborated on incorporating the Stealth technology into marketable toilets.

I installed a Stealth yesterday and there isn't much to report. If a user didn't know how little water it uses, he/she would think it was a regular toilet. The Stealth flushes a little better than the 1997 1.6 gpf model it replaces and sounds about the same.

If we can just get them to treat the bowl with a self cleaning feature like the easy care glass we've been using on windows and is now available on shower glass we'll have a serious home run, self-cleaning ultra-low-flow toilets with a large water spot.

Sounds great. This unit would seem to put more emphasis on the operation and maintanance of the seals in the flush system. On regular gravity systems these seals can be a problem and are almost never replaced. How has the unit fared in longer term tests as far as leakage? How much are replacement seals and how hard are they to replace?

5.
May 28, 2010 7:18 AM ET

Pitch by Anonymous

Remembering the problems when NYC went to the 1.6 gal flush in older buildings, a large amount of stoppages were created which gave us the power assist units in comercial use. The pitch then went from 1/8 per foot to 1/4 per foot. I dont feel the wash out will be enough to carry to the main stack as well as into the house drain. I would like to see more research and tests to see the long range effects

6.
Nov 23, 2010 3:18 PM ET

Stealth Works Better than any wc ever by Joseph Cincotta

It really flushes thoroughly and consistently. It is also the most quiet flush ever. Better than any toilet. we have Kohler, Toto and Am Standard and Gerber. This is the top. The manufacturer's argument that public wc's rarely are used in the lower flush mode is compelling.

We've had an elongated stealth for over two months and can attest to its efficiency. We have other power assisted toilets and they use more water and are so noisy. The water surface area on the stealth is pretty good so the need for cleaning is typical. We'll be buying another stealth soon.

9.
Jan 21, 2011 1:31 PM ET

Stealth sides by Elaine

Love the function!
Please tell me there is a slick sided toilet available? Keeping 3 toilets clean when the sides gather dust and other grunge, is a full time job.....

10.
Oct 26, 2011 6:19 PM ET

Stealth Sides by chris pfohl

Yes but it is the TOTO Aquia. .9gal with no exotic hardware to break down. It is a Dual Flush so solids have sufficient water (1.2g?) to keep the lines clear. Works superbly (2 units installed at home 3 years ago).

About the Authors

Peter Yost is the Director of Residential Services for BuildingGreen, LLC in Brattleboro, Vermont. He has been building, researching, teaching, writing, and consulting on high performance homes for more than twenty years. Read more...

Alex Wilson is founder and executive editor of BuildingGreen, LLC in Brattleboro, VT. He is coauthor of the Consumer Guide to Home Energy Savings (9th edition, 2007) and author of Your Green Home (2006).